The present invention relates to a turbojet engine nozzle of the two-dimensional, adjustable cross-section type.
Adjustable turbojet engine nozzles are well known in the art and comprise either a two-dimensional adjustable type, or a type formed by an annular ring of adjustable flaps. Typical examples of such annular rings of adjustable flaps can be found in French Application No. 2 602 274 as well as U.S. Pat. Nos. 4,641,783 and 4,817,871. The objective in each of these structures is to obtain the optimum jet thrust, while also assuring adequate performance in the area of specific fuel consumption. These objectives are achieved by adjusting the cross section of the nozzle to obtain optimum thrust and specific fuel consumption for each specific operational condition of the jet engine.
For certain applications, the two-dimensional adjustable nozzle type has proven to be beneficial over the annular ring of adjustable flaps due to its less complicated and simpler construction which reduces the production and maintenance costs of jet engines incorporating these types of nozzles. The two-dimensional adjustable nozzles typically comprise a pair of opposite, fixed walls defining the lateral boundaries of the nozzle and a pair of opposite, adjustable flaps defining the upper and lower boundaries of the nozzle. The cross section of the nozzle is adjusted by varying the angle of the adjustable flaps. Typical examples of this type of nozzle can be found in European patent application 0 180 534 and U.S. Pat. No. 4,778,109.
Since the number of flaps in the two-dimensional adjustable nozzle is less than the number of flaps in an annular ring of adjustable flaps, and, consequently, the area of the flaps are larger, the pressures exerted on the flaps by the exhaust gases passing through the nozzle are greater than those in the multi-flap annular ring nozzle. This has required two-dimensional nozzles to be structurally reinforced to withstand the increased gas pressure forces. This has resulted in the structures becoming unduly heavy, since such reinforcement must also compensate for the increased stress concentration points caused by the generally rectangular shape of such nozzles.